Bridges

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Bridges

• Materials
• how to use them

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Why?
The AP6 module has got a lot of Mechanical Design
in it. You dont have to DO it, but you need to
understand some basic design concepts and
appreciate that ENGINEERS use SCIENCE to make
things that WORK and that are SAFE.
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Bridges come in 5 basic sorts. All these below
are truss. The components of a truss bridge are
either in compression or tension.
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In the pictures that follow, just try to imagine
what forces are holding this bridge up.
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Somebody must recognise this bridge. Where is it?
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Beautiful Railway Bridge of the Silv'ry
Tay!Alas! I am very sorry to sayThat ninety
lives have been taken awayOn the last Sabbath
day of 1879,Which will be remember'd for a very
long time.
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Bouch had bad health problems at the time of the
design of the Tay Bridge and his actions appear
as a man who has lost the place.  His correct
action should have been to tell his clients that
unless they were prepared to spend adequate sums
to build a safe bridge he would hold them
responsible for the consequences.  But of course
it was his responsibility to build a safe bridge
and if his clients would not let him do this he
should have resigned from his commission from
them.  Not an easy, but a sometimes necessary,
course of action. Bouchs situation has
resonances for modern construction.  Clients
still try to pressure consultants to cut costs
and hence reduce safety.  The professional
engineer must not buckle to such pressure.